<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>form 表单提交第一个实例</title>
    <style>
        .error {
            color: #FF0000;
        }
    </style>
</head>
<body>
<form action="welcome.php" method="post">
    名字: <input type="text" name="fname">
    年龄: <input type="text" name="age">
    <input type="submit" value="提交">
</form>
<br>
<br>
<br>

<?php
// 定义变量并默认设置为空值
$nameErr = $emailErr = $getderErr = $websiteErr = "";
$name = $email = $gender = $comment = $website = "";

if ($_SERVER["REQUEST_METHOD"] == "POST"){
    if (empty($_POST["name"])){
        $nameErr = "名字是必须的";
    }
    else
    {
        $name = test_input($_POST["name"]);
        // 检测名字是否只包含字母跟空格
        if(!preg_match("/^[a-zA-Z]*$/",$name)){
            $nameErr = "只允许字母和空格";
        }
    }

    if(empty($_POST["email"])){
        $emailErr = "邮箱是必须的";
    }else{
        $email = test_input($_POST["email"]);
        // 检测邮箱是否合法
        if (!preg_match("/([\w\-]+\@[\w\-]+\.[\w\-]+)/",$email))
        {
            $emailErr = "非法邮箱格式";
        }
    }

    if (empty($_POST["website"])){
        $website = "";
    }
    else{
        $website = test_input($_POST["website"]);
        //检测 URL 地址是否合法
        if(!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)
        [-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)){
            $websiteErr = "非法的 URL 的地址";
        }
    }

    if(empty($_POST["comment"])){
        $comment = "";
    }
    else
    {
        $comment = test_input($_POST["comment"]);
    }

    if(empty($_POST["gender"])){
        $genderErr = "性别是必需的";
    }else{
        $gender = test_input($_POST["gender"]);
    }
}

function test_input($data){
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
}
?>

<h2>PHP 表单验证实例</h2>
<p><span class="error">* 必须字段</span></p>
<form method="post" action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']);?>">
    名字: <input type="text" name="name" value="<?php echo $name;?>">
    <span class="error">* <?php echo $nameErr;?></span>
    <br><br>
    E-mail: <input type="text" name="email" value="<?php echo $email;?>">
    <span class="error">* <?php echo $emailErr;?></span>
    <br><br>
    网址: <input type="text" name="website" value="<?php echo $website;?>">
    <span class="error"><?php echo $websiteErr;?></span>
    <br><br>
    备注: <textarea name="comment" rows="5" cols="40"><?php echo $comment;?></textarea>
    <br><br>
    性别:
    <input type="radio" name="gender" value="<?php if (isset($gender) && $gender=='female') echo 'checked';?>">女
    <input type="radio" name="gender" value="<?php if (isset($gender) && $gender=='male') echo 'checked';?>">男
    <span class="error">* <?php echo $genderErr;?></span>
    <br><br>
    <input type="submit" name="submit" value="Submit">


</form>

<?php
echo "<h2>您输入的内容是:</h2>";
echo $name;
echo "<br>";
echo $email;
echo "<br>";
echo $website;
echo "<br>";
echo $comment;
echo "<br>";
echo $gender;
?>

</body>
</html>